The present invention generally relates to an image data transmission method and apparatus. More particularly, the present invention is directed to a facsimile communication method and a facsimile machine based on the same.
Generally, a facsimile machine is required to transmit image data of high quality. For this purpose, the facsimile machine has various image correction processes which are carried out for an image signal obtained by a document reading system. Examples of those processes are a shading correction process, an MTF (Modulation Transfer Function) correction process and .gamma.-correction process. The shading correction process intends to suppress dispersion of density in the direction of a document reading line. The MTF correction process intends to correct a faded image. The .gamma.-correction process intends to correct tone in reading a halftone image. The above-mentioned image correction processes are disclosed in Japanese Laid-Open Patent Application No. 62-186663, 62-186664, or 62-186665, for example.
Generally, quality of image transmitted from a transmitter is evaluated by an operator on the side of a receiver which receives the transmitted image and reproduces the original image. Generally, an image recording (printing) system provided in a facsimile has an image recording characteristic. Therefore, an image reproduced (recorded) from the received image data depends to a large extent on the image recording characteristic of the image recording system of the receiver fascimile machine.
That is, conventionally, an image correction process based on characteristics of the document reading system is executed in the transmitter facsimile machine, and on the other hand, no image correction process based on characteristics of the image recording mechanism is executed in the receiver facsimile machine. If the image correction process on the transmitter side does not match the image recording characteristic on the receiver side, the quality of reproduced image is not good. Particularly, the above disadvantage is conspicuous in a case where image recording resolution of the receiver side is high and thus the receiver is capable of outputting a reproduced image of high quality.